From on, several different coding systems were used, from which the manufacture date and often the assembly date can be decifered. For pre Schwinns try taking out the crankset to check for a date code. We are in the process of collecting pre serial numbers in the hopes of rebuilding the date code system for this period. Pre B Z Schwinn's built-in kickstand was introduced in The DX style frames have a lower top-tube for lack of a better name that curves ever so slightly, however the chainstays on the Schwinn D97XE-OS run roughly parallel to the ground while the chainstays on the D97XE-6 and the D droop slightly as they travel from the rear dropouts to the bottom bracket. The -OS frame style seems to have been completely replaced by the more curvaceous -6 style by
Vintage Schwinn Bikes
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Classic Lightweights UK Restoration. In these cases examination of the frame number — where it is, what it is, and how it is, may be of some assistance at least in allowing other specialists to hazard a guess at the true origin of the frame or machine. These publications have been invaluable in adding accuracy to the information — but even including their data there are still well over makes of possible lightweights to be confused over! The author would be grateful to know of any inaccuracies and to receive further information to make the tables more comprehensive.
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Trek frame serial numbers SNs are typically stamped into the bottom of the bottom bracket shell. In the case of some early 80s Treks, the number is under the plastic cable guide on the bottom of the shell. Just remove the plastic cable guide to see the number. The other place Trek or their subcontractors stamped the SN is at the lower end of the seat tube.
Note that the serial number information below is fragmentary and incomplete, and many bikes have proven to be much newer than the serial numbers would suggest. It appears that Raleigh recycled many of the older serial numbers in later years, so there are lots of bikes from the 60s and 70s that have serial numbers that would suggest much greater age. Most older Sturmey-Archer hubs have two or three-letter model codes, which are usually stamped onto the hub shell. Conveniently, they also usually have the month and the last two digits of the year of manufacture stamped onto the shell.